Very stable resole-type phenolic resin emulsions have been conveniently formed using protein type emulsifiers. However, these type emulsifiers cannot be used with resole solutions containing polyvalent cations such as calcium, barium and strontium. This has limited the choice of catalysts and salts that can be employed in the manufacture of phenolic resins containing proteins unless the cations are removed prior to protein addition. This limitation can be undesirable to both cost and manufacturing convenience.
During the normal manufacture of resole-type liquid phenolic resins a basic catalyst is utilized. To stabilize the finished resin, the base is usually neutralized at the end of the manufacturing process. The neutralization results in the formation of either a soluble or insoluble salt depending on the base catalyst and neutralizing acid employed. Since the presence of excess salt can be deliterious to certain end use properties, it is often removed from the resin by techniques such as insoluble salt filtration or ion exchange. From both a cost and pollution criteria, it is desirable to avoid removing the salt from the resin. However, if the salt is left in the resin it ideally should be of a type that does not degrade end use properties and that may even enhance end use performance.